Some people have said that when they try to click on a forum thread within another forum thread (example below) that they don't get to that specific thread topic. it actually takes you to the main forum page and not the one that you wanted to go to.
doesn't seem to be happening for non-dkpsystem site links, just within it. I linked a random link from your site to see if it's the same thing here.
https://www.dkpsystem.com/forum.php#threadid=7043&p=1